The long-term objectives of this program are to develop and manufacture a low-cost in-situ sweat determination system for cystic fibrosis (CF) screening in children and infants. Using the proprietary technology of Integrated Ionics Inc., an accurate temperature corrected sodium and chloride determination can be performed by placing a miniaturized combined sweat collection/sensor unit onto the skin of the subject. The sensors will be mass fabricated using semiconductor-based electrochemical sensors with integrated electronics. The aim is to determine the feasibility of such a system, preferably without the need for sweat induction. A Phase II effort will then be proposed to develop the sensor unit and portable recording unit to a point where the system can be manufactured and marketed. The study will use the Gibson-Cooke pilocarpine iontophoresis determination as a reference method. The proposed test will use 1 Mul of sweat in a determination lasting five minutes and requires lesser skilled staff, which will make it appropriate for even neonatal screening. The commercial potential would be over 4 million sensors per year in the U.S., plus a further 6 million in Europe for CF screening alone. Other applications are also envisaged, for example, in hormonal research.